Percutaneous Catheter System and Method for Rapid Diagnosis of Lung Disease

ABSTRACT

A percutaneously delivered medical device and its method of use includes a catheter, at least two electromagnetic sensing coils located within the distal tip of the catheter, and at least one within the proximal handle, and a multi-element planar ultrasound transducer array located within the distal tip of the catheter and configured to transmit and receive ultrasonic energy in at least two imaging modes. The device also includes an imaging system coupled to the ultrasound transducer and is used for creating an image of tissue in a first target plane that extends orthogonally from the catheter body. The medical device also includes a backscatter evaluation system for use in receiving and evaluating the acoustic spectral characteristics of tissues within a second target area within the first target plane.

CROSS-REFERENCE TO RELATED CASES

This application is a utility application claiming priority to provisional application Nos. 62/776,677 and 62/776,667, of which both were filed on Dec. 7, 2018, and whose entire contents are incorporated herein by reference.

FIELD OF THE INVENTION

A medical device catheter system integrating both electromagnetic navigation and ultrasonic imaging and backscatter evaluation for use within the lung to provide a diagnosis of cancer. The embodiments shown is used with a percutaneous access device.

BACKGROUND OF THE INVENTION Current Standard for Lung Cancer Diagnosis

At present conventional cancer protocols call for the collection of physical samples (biopsy) of suspected tissue uncovered during routine examination (X-ray, CT). The biopsy samples are sent to a laboratory for microscopic evaluation and it is the laboratory pathologist who declares the pathology of the sample making the diagnosis of the disease.

Next the patient and his physician select an appropriate treatment regime, which may include surgical resection, chemotherapy, or ablation in the case of lung cancer. If the tissue presents as advanced lung cancer then palliative and hospice care are indicated. If the tissue presents a case of chronic obstructive pulmonary disease (COPD) or other disorder an appropriate treatment regime will be selected. If the tissue is normal no intervention is required.

This traditional diagnostic methodology occurs over several medical intervention sessions that may need to be repeated to verify diagnostic features of the disease, which is undesirable. This traditional methodology also has low diagnostic yield. Many disease cases are missed especially in early stage lung diseases that are the most readily treated. Also occasionally a misdiagnosis results in unnecessary intervention.

Current Technologies used for Assessing Lung Disease

The application of Electromagnetic Navigation (EM) to lung bronchoscopy began in the early 1990s. Veran Medical Technologies has developed a set of catheter systems that may be used with a bronchoscope or through the chest wall to accurately target and reach very small tissue masses. Biopsy tools may be delivered to the target mass through the catheter system to collect a physical sample of tissue for analysis. This technology is described in detail U.S Pat. No. 8,696,549 entitled Apparatus and Method for Four Dimension Soft Tissue Navigation in Endoscopic Applications. This document is incorporated by reference herein. Some systems are implementing image matching, electro-potential and fiber optic localization and can be used an alternative localization technologies.

This is the current state of the art Electromagnetic Navigation assisted lung navigation. In general, a preoperative Computed Tomographic X-Ray (CT) scan is used to build a model of the airways within the patient. Electromagnetic sensors (EM) sensors on the indwelling catheter are very small and provide location and orientation information for the catheter tip in three space (3D). The Veran system also provides a fourth dimension of time varying tracking information. Respiratory tracking is available in the Veran system and this is effective in altering the apparent position of the probe in the virtual display to match the physical location of the EM sensors as they move with the body's respiratory motion, which is very useful in the present device.

For purposes of the present invention the ability to translate a known position in three space and to accurately reference this know location into an image space created from CT or other imaging modalities allows precise knowledge of the exact location under ultrasonic evaluation.

At present devices that apply ultrasonic imaging to lung bronchoscopy instruments are well known and offered by several manufacturers. These Endo-Bronchial Ultrasound Systems (EBUS) allow the operator to look outside of the airways using radial or conical ultrasound imaging sensor on a catheter that passed through the bronchoscope. The typical field of view is intentionally quite large, usually 360 degrees, and quite deep, to survey the maximum amount of tissue possible. The image with its anatomic detail, is typically used by the physician for navigation. Targets of interest are defined solely by the image characteristics and accessed by biopsy tools delivered to the target site through the EBUS catheter.

Clinical applications of conventional ultrasound incorporate many imaging modes, such as gray-scale “B-mode” imaging to display echo amplitude in a scanned plane; M-mode imaging to track motion at a given fixed location over time; duplex, color, and power Doppler imaging to display motion in a scanned plane; harmonic imaging to display non-linear responses to incident ultrasound; elastographic imaging to display relative tissue stiffness; and contrast-agent imaging with contrast agents to display blood-filled spaces or with targeted agents to display specific agent-binding tissue types. A less well- known ultrasonic technology is based on quantitative ultrasound or (QUS), which analyzes the distribution of power as a function of frequency in the received echo signals backscattered from tissue; QUS exploits the resulting spectral parameters to characterize and distinguish among tissues. Another potential imaging technology involves applying AI techniques such as Convolutional Neural Networks at various stages of the imaging pipeline to characterize tissue based upon training dataset. This AI assisted evaluation of image data may speed the overall diagnosis, which is desirable.

SUMMARY OF THE INVENTION

In the view of the inventors a set of acoustic measures along with patient medical history can be used to declare a nodule or other tissue type sample cancerous. It is expected that nodules or any tissue type will be amenable to this acoustic measurement method or process. This evaluation is expected to be as accurate and on par with conventional pathology evaluation. It is possible to add artificial intelligence system to combine data from several sources. For example, another potential imaging technology involves applying AI techniques such as Convolutional Neural Networks at various stages of the CT and US imaging pipeline to characterize tissue based upon training dataset. This AI assisted evaluation of image data may speed the overall diagnosis, which is desirable.

The catheter and associated systems of this invention allow targeted tissue to be accessed and identified and characterized in situ during the intervention. This diagnostic data is taken all at the same time and at the same location. This synoptic data set can be combined with other data and conventional medical judgment to reach a treatment decision immediately. The approximate target tissue location is reached in a conventional fashion by inserting a percutaneous access needle into the lung, through the skin, and then observing and navigating the needle and transducer by following the needle in the lung model that is based upon and created from a pre-op CT scan. The user manipulates the catheter through the needle, and electromagnetic (EM) navigation is used to approach the target tissue location through visualization of the lung tissues in the model image space presented to the physician on a monitor. The location information from the navigation system shows the physician where in the derived lung model he is located. Ultrasonic imaging (US) is then used to define a first target plane or a first target volume of the tissue of interest and its precise location. Next the user defines a reduced version of this target volume containing a homogenous sample of tissue. This second reduced target plane or reduced target volume is selected so as to excludes irrelevant anatomic structures and produce an image plane or image volume that represents a homogeneous sample of suspected tumor tissue. The second reduced target is evaluated using what amounts to an acoustic biopsy by implementing QUS techniques. The overall catheter system allows for the placement of a physical biopsy sampling tool. This tool, for example a needle or brush, is then placed at the same identical target site that was evaluated acoustically and a tissue sample taken from the same tissue subjected to the acoustic biopsy.

As suggested above, the ultrasound system has two modes of operation. A first imaging mode displaying slicewise a relatively large first target area and a second quantitative spectral evaluation mode selecting backscattered radiation from a second reduced target area.

The ultrasound imaging system provides a controlled view around the catheter distal tip. The preferred embodiment of the ultrasound transducer is a planar array fixed into position within the distal tip of the catheter. The planar array may be used in a synthetic aperture mode constructing a displayed image plane formed from data taken a several locations at several times while the catheter body is stationary. It is possible to move the catheter translate from a first location to a second nearby location. Catheter motion may be used alone to exclude anatomic structures form the second reduced target area. The motion of the catheter creates a swept volume for use in image contraction or backscatter evaluation.

Typically, the field of view of the ultrasound transducer will be 60 degrees or less, but as suggested above it may be rotated or translated mechanically or manipulated electronically to control the size of the field of view. The depth or range of the field may also be limited in contrast to the typical EBUS system where a large view of extensive tissue is desired. Usually the US view will encompass several tissue types. Medical judgment is used to tune and to position the catheter system near the target tissue to isolate the target tissue of interest for acoustic biopsy from other anatomic features such as blood vessels and the like. In this fashion medical expertise selects a first target area encompassing the suspected tumor tissue. Next a subset of the initial first target volume is selected for backscatter analysis. This second reduced target area will be selected to be free of extraneous anatomic structures and provide a relatively homogenous tissue sample to provide backscatter suitable for spectral evaluation.

With the position of the acoustic biopsy noted by the EM location portion of the EM navigation system an integrated biopsy sample device may be directed to the acoustic biopsy location. This needle tip placement can be done with very high precision as it is calculated with knowledge from the EM sensor 4D location information.

Thus, and in practice the US system is used to image a volume of tissue, called the first target area, and then the operator manipulates the catheter system to isolate a second reduced target area to contain tissue of interest within the smaller field of view of the quantitative mode of ultrasound sensor operation. With the tissue isolated the acoustic backscattered radiation is evaluated to discern the nature of the tissue. By using QUS tools the very small sample is effectively subjected to an “acoustic biopsy “or “sonic biopsy” that is performed in situ, and at a known location that can be re-accessed to provide a therapy if required.

Furthermore, QUS can be used to analyze the tumor stroma and microvasculature nature to provide parameters related to cell death and/or apoptosis to provide confirmation or monitoring data of therapies such as chemotherapy, brachytherapy, cytotoxic agents (drugs) or ablation. This analysis can provide interim feedback of a tumor's response to therapy using parameters such as effective scatter diameter and effective acoustic concentration. The heterogeneity of a tumor or tissue stiffness can be analyzed by evaluating a nodule from multiple different directions and determining the depth of penetration of the ultrasound signal.

With the ability to create a 3D or 4D ultrasound image of the nodule. The user is able to compute both a nontextured and texture parameters for the 3D or 4D image. Non-texture features such as size, shape and location descriptors relative to adjacent structures (pleura, fissures, vessels, etc.) can be defined in ultrasound space. Additionally, texture-based features such a pixel intensity histogram and run-length (contiguous similar grey levels or RF levels) and co-occurrence to define a metric of fine to coarse tissue. Co-occurrence metrics such as contrast, energy, homogeneity, entropy, mean and maximum probability can be used to characterize the tissue in the nodule, Images can be decomposed in orthogonal components to provide wavelet features for these images. Kernels can be applied to reflect or highlight a specific or different type of structure in the images. Applying multiple kernels based on multiple orientations can be used to characterize the tissue of the nodule. AI techniques may be used to augment texture-based classification in the image domain.

The exemplary US system uses piezoelectric transducers fabricated using modern micro-machining techniques. In general the array of individual transducer elements are addressable and may be activated individually. Typically the array will include elements sized to operate a particular resonant frequency. Although a single frequency array is possible it is expected that the array will have elements operable at least two frequencies. The elements may be considered to have a diameter and depth sometimes called a drum size, and like a drum each element will have a resonant frequency associated with its geometry. In general there are many fabrication alternatives for producing ultrasonic transducer arrays including PZT, pMUT or cMUT based devices. It is expected that any of these could be used to collect the tissue information. There are trade-offs to be considered and it is desirable to maximize the fractional bandwidth of the devices. Having a common or consistent characterization for different tissue types can either be achieved through a calibration of the transducer to a known performance characteristic or implemented using repeatable performance provided from an integrated circuit such as a pMUT. This normalization is key to providing repeatable identification of the tissue. The system can allow for varying frequencies of the ultrasound transducer and therefore capture tissue data at multiple frequencies (4 to 50 MHz). Imaging may be optimized for 20 MHz while the acoustic biopsy may be acquired at a different frequency that will typically be higher.

Current US systems have the limitation of decreasing resolution in the lateral direction which creates a varying signal depending on the distance the tissue of interest is from the ultrasound transducer. The array construction of the ultrasound transducer provides increased, consistent resolution in the lateral direction for the complete field of view (FOV) or across varying depths from the transducer.

The US system with integrated EM localization allows 3D and 4D ultrasound volumes to be collected by recording multiple ultrasound image planes and reconstructing the volume. These volumes can be respiratory gated to have multiple volumes created at the same tissue location of interest (i.e. tidal volume inspiration, tidal volume expiration, or interim states along the breathing cycle). These volumes can be at multiple states of processing from raw electrical signal data to beam formed B-mode image data for analysis.

The integrated EM sensor allows for sampling the same tissue of interest from multiple viewpoints or angles to therefore determine the variation or change based on the viewpoint. Avoiding structures such as blood vessels, fissures or surrounding infection will provide a cleaner acoustic biopsy and can be used to determine the quality of the acoustic biopsy collected based on interference from other structures.

In order to get the ultrasound transducer as close to the tissue of interest as possible it is important to miniaturize the device to be less than 2 mm in diameter and short as possible to make tight turns to maintain flexibility of the catheter through the patient's airways. In at least one embodiment the array has at least 64 imaging elements but other configurations from 16 to over 256 could be operable. These multiple imaging elements are multiplexed to allow for the fewest wires possible to drive the US transducer while maintaining a frame rate of 20 to 30 frames per second.

Using the EM system and registered CT data, provides for correlated multiple modality images that can be for enhance interpretation. Additional modalities such as PET-CT can be registered to identify tissue of interest. The ultrasound image provides additional data points other than the EM system that can be used for deformation of pre-operative or intra-operative images. Not only the pathway that can be recorded as a point cloud, but a pathway volume outside the airway can be collected as part of the point cloud.

Models to estimate the probability of malignancy in patients with pulmonary nodules using clinical profile, demographic and imaging data (CT, FDG-PET, growth rate) such as the Gurney, Mayo Clinic, Herder, Va., Peking University People's Hospital, Brock University, Thoracic Research Evaluation and Treatment, and Bayesian Inference Malignancy Calculator are well known. While they do provide the physician input, they are not sufficient to definitively determine if a nodule is malignant. Additionally, radiomics has been applied to CT images to further provide a likelihood of malignancy based on the CT image data. This US system with an integrated EM capability enables the ability to register the CT and FDG-PET image data to the patient and correlate the US, CT and FDG-PET image data simultaneously at the precise location within the patient. Additionally, bronchoscopic image data (color variation of tissue) created by infrared, ultraviolet and visible light. A pressure sensor may also be integrated to provide pressure data for the tissue of interest. Another type of sensor may be included in the device for example a temperature sensor can be integrated to determine the temperature change between tissue and the tissue region of interest. An oxygen sensor can be integrated to determine changes in the oxygen levels between the tissue. Other types of sensor may be used to monitor the metabolic characteristics of the tissue. This extra sensor value may be used to help determine the presence of cancer.

It is understood that this device is not limited to the lung and may be used for multiple organs (lung, liver, kidney, prostate, soft tissue, pancreas, etc.). Pathways to get to the tissue of interest can be airways or blood vessels or direct percutaneous access, or access through a natural orifice. It may also be used for therapy confirmation as well as nodule diagnosis.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the catheter located in a percutaneous access needle;

FIG. 2 is a cross section view of an alternative handle for the proximal end of the catheter;

FIG. 3 is a perspective view of the distal tip portion of the catheter system;

FIG. 4 is a cross section of the distal tip of the catheter;

FIG. 5 is a schematic block diagram of the electronic portioning of the systems;

FIG. 6 is a schematic view showing the first target image plane

FIG. 7 is a schematic view showing the reduced second target image plane;

FIG. 8 is a spectral diagram showing illustrative acoustic parameters for QUS.

DETAILED DESCRIPTION OF REPRESENTATIVE EMBODIMENTS

FIG. 1 is a perspective view of the catheter assembly 14 located in a percutaneous access needle 10. The elongate catheter body 18 extends from the distal tip 16 seen best in FIG. 3 to the proximal handle 12 seen best in FIG. 1. An alternative handle 9 with an axial cable 7 is seen in FIG. 2 in contrast to the lateral cable 15 route of handle 12. Typically, the physician will advance the distal tip 16 out of the needle 10 by pushing the handle 12 relative to the needle base member 11. The trocar end of the distal tip seen at 19 may then be used to take a sample of tissue such as that of a lymph node, lung tissue, etc.

FIG. 2 which shows an alternate handle 9 construction with the cable 7 aligned with the long axis 21 of the catheter body 18. The handle 9 in FIG. 2 shows an elongate sensor coil 37 located in the handle proximal end along axis 47. This sensor coil 37 is orthogonal to at least one sensor in the distal tip 16 shown in superposition in FIG. 2 at reference numeral 39. At least one more sensor is located in the tip as well illustrated by the superposition of coil elements 33 and/or 39. In use and in combination with the distal coils 33, 35 and/or 39 the navigation system can report and display the angular relationship of the catheter body to the physician. That is the display will show the orientation and direction of travel for the catheter system 14 in real time.

FIG. 3 is a perspective view of the distal tip in isolation showing the cylindrical orientation of the ultrasonic array 30 just proximal of the trocar end 19.

FIG. 4 is a schematic cross-section of the distal tip 16 showing a planar array wrapped around a shell 17 thus forming the cylindrical array 30. The gap 31 shows the seam of the array 30. The array 30 includes multiple transducer elements of which two are shown as elements 41 and 43. The EM coils (e.g. coils 33, 35 and 39 shown in FIG. 2) are placed behind or proximal of the array 30 and cannot be seen in this cross section view. A lumen 38 is centrally positioned to receive a guidewire therethrough.

FIG. 5 is a partitioning of the electronic componentry in an illustrative but not limiting version of the system.

The electronic package 34 will contain among other things a programmable chip to configure the array 30. A multiplexer will format and transmit data from the catheter system to the patient interface module PIM 42 , which will be hung bedside on the gurney with the patient. The PIM 42 includes electrical isolation to protect the patient and also contain power supplies for the catheter itself , A/D conversion and various buffering processes are accomplished in the PIM to improve noise performance of the catheter. In this implementation a separate “pizza box” enclosure 44 carries dedicated hardware for the synthetic aperture beam forming and control as well as the spectral analysis of the backscattered signals for the QUS processes. The enclosure is coupled to the workstation based navigation and display cart. It is expected that the content of the pizza box enclosure 44 will be incorporated into the workstation 46 itself in further iterations of the product.

The catheter body 18 has a matrix of individually addressable piezoelectric transducers elements, of which two are depicted in FIG. 4 as elements 41 and 41, which are fabricated into an array 30 using micromachining technology. Each element of the array can be powered to emit ultrasonic energy as a spherical wave emanating from the specific transducer location, and each element in the array can function as a receiver transducing the mechanical energy of backscattered sound into a an electrical signal. Once a wave is launched from a given element, such as element 41, a companion transducer, such as element 43, can detect the backscattered energy reflected off of biologic tissues. In the synthetic aperture scenario only one transducer is listening to the transmitting transducer element at a time.

In general pairs of elements will be activated with one element 41 functioning as a transmitter of acoustic energy and the companion element 43 functioning as a receiver. Since the elements are arrayed in space several viewpoints are present in the array. This provides much improved lateral resolution when compared to prior art approaches.

With that data stored, a next transducer in the array is activated to transmit acoustic energy and its complimentary transducer receives the backscattered return signal. With many, for example 64 transducers, at various locations, the composite of all the returned energy from all the locations can be used to form though computation an image plane orthogonal to the plane of the transducer. It is possible to have more than one transducer pair active at a time and in the exemplary embodiment 4 channels of data are collected synchronously. The limitations are based on complexity and power dissipation and bandwidth of the data paths. Consequently other configurations are possible and anticipated within the scope of the claims. The mathematics to pull an image in a plane from the time sequenced multiplex data that is transmitted and received at various points in space is complicated but well known and understood in the field although not by your author. In general the displayed image plane is synthesized from data taken at many locations in space taken at different times, that are collectively convolved into a single image plane hence the term synthetic aperture. If one moves the catheter along a path the synthetic aperture image plane sweeps out a volume. This is a relatively low resolution image of a volume of tissue but can help to resolve the extent of anatomy to supplement the detection of anatomic structures such as airways, blood vessels, and the like in the 2-D first image plane area. In this regard the methodology of the invention may rely on a first target image area in a plane or rely on a 3-D volume called the first target image volume. In this later case catheter movement is used to define the first 3-D volume of target tissue.

In use there are two modes of operation for the ultrasound transducer array. In a first mode, the amplitude and envelope information from the backscattered acoustic energy is used to form an image presented to the clinician. This may be a first 2-D slice of target tissue or a 3-D volume of target tissue. In a second mode the transmitted power is reduced to select a smaller target plane or volume within the first image plane or image volume. This reduced view is called the second reduced area or slice in the event of a 2-D slice or a second reduced volume in the event of a 3-D volume. In each case the reduced view is selected to be free of anatomic detail observed in the first view. The exclusion of gross anatomic structure selects a homogenous sample for quantitative analysis. The spectra of the backscattered energy from the reduced area slice or volume is evaluated quantitatively and automatically rather than used to form an image. The image free quantitative information is used to determine if the reduced area of tissue exhibits the acoustic characteristics of cancerous tissue. The precise characteristics or the acoustics of cancer is a topic of study at the present time.

FIG. 6 shows a portion of the catheter assembly 14 without the access needle to facilitates discussion of operation of the device. The catheter body 18 is shown in situ in a patients lung, with the distal tip located at position “1” marked 60 in the figure. The first target plane 62 show in light hatch is an image plane intersecting a suspected tumor mass 64 that lies near an airway 66 and is crossed by a blood vessel labeled 68 twice in the figure. This image mode ultrasound data is used to find the suspect tumor mass and to verify and note its location.

FIG. 7 shows the catheter body 18 repositioned or moved slightly so that the backscatter associated with reduced target plane 72 does not intersect the blood vessel or airway. This is the reduced second image plane used for backscatter evaluation for QUS.

FIG. 8 shows a spectral graph of normalized reflected acoustic power on the Y-axis and the corresponding frequency on the X-axis. Squares typified by square 100 depict the amplitude of reflected power at the corresponding frequency. One can draw a “best fit” line 102 through the various data typified by data point 100. The slope of this line is a useful parameter and is identified on the figure at 104. The point where the best fit line 102 crosses the y axis is the Y-intercept 88. If one excludes both high and low frequencies defining a mid-band the arithmetic average of the remaining values' forms the mid band fit value 86 shown on the figure.

Calibration and Alternative Embodiments

In general the ultrasound spectra will be normalized to perform the QUS parameters. However the absolute energy in the reflected signal has diagnostic value alone and it is expected that the not normalized spectra will be used clinically as well. For this reason among others it will be important to calibrate individual catheter sensors. The ultrasound transducer technology as well as fabrication methodology results in widely varying sensitivity and other acoustic properties. It is anticipated that each sensor will be characterized during the manufacturing process to generate a compensation profile for the sensor over its entire operating range. This unique calibration table will be stored onboard the catheter is an appropriate read on memory.

It is generally preferred to have a radial US transducer to carry out the inventive steps, however as an alternative the sensor could be a linear structure forming a pie shape field of view. Also this pie shaped field of view ay be stepped around a circle either mechanically or electronically.

An additional EM sensor may be paced in the handle and this proximal EM sensor system may be used with the EM sensor array in the distal tip to translate physician motion which affects the sensors to provide information and feedback to the physician about the orientation of the catheter system. In this version the relative motion or position of the two EM sensors along with the known geometry of the catheter allow for the computation of the location of the tip or another attribute of the catheter.

Note that there are several independent US transducers along the length of the distal tip of the catheter. Each US transducer forms a separate station. In this configuration the catheter need not be moved to survey an extended volume of tissue. In use each US station may form an image plane that is relatively small. The sensor transducer stations may be adjacent to each other or spaced apart. Acoustic energy backscattered from this image plane is interpreted as both an image as well as subjected to QUS interpretation for tissue characteristics. By engaging all transducer at the same time or engaging them separately the operator can get an estimate of the size of the lesion of interest.

The single plane configuration of the percutaneous US needle will create a single image plane using a single 16 to 64 element ultrasound transducer ring around the needle. Additionally multiple similar rings can be added to the needle to produce a 3D ultrasound image volume from multiple image planes. The device can be sequenced in numerous patterns to create image, the most basic being send on one element and listen on multiple adjacent elements on the same ring. It is also possible to send on one ring and listen on multiple rings on the same side of the needle.

The rings could either be side by side or spaced apart to create different sampling and imaging capabilities. In an acoustic biopsy application, the ability to collect backscatter RF energy from multiple angles simultaneously about a single location in the tissue is advantageous. This enables the ability to have correlated QUS data instantaneously at a location in the tissue. Having two rings 5-10 mm apart creates significantly different RF signatures for the single tissue location on each ring due to differentiated tissue and anatomy in the acoustic path.

The available transducers of a multi-element array will also allow the transmit and receive functions to be carried out at differing locations. It is expected that this will increased the quality of analysis.

It should be noted that the backscattered radiation may be normalized with respect to the acoustic energy delivered to the tissue or the actual absolute value of the radiation may be evaluated. There is evidence that the total absorption of acoustic radiation of tissue has diagnostic value.

In general the analog nature of the transducer technology as well and the relatively long signal paths can be addressed by a calibration process during transducer manufacture. It is expected that each catheter will be calibrated and calibration information stored along with unit ID in a read only memory integrated in to the catheter product.

Although described with regard to representative embodiments various departures and additions may be made without departing from the scope of the invention as expressed in the claims. At least one embodiment of the present percutaneously delivered catheter system and its method of use may be described as follows:

A catheter assembly 14 is shown in FIG. 1 that is operated by a physician user (not shown) who percutaneously advances the catheter assembly into a patient's lung tissue having a suspected tumor (via needle 10). The assembly comprises a catheter body 18 terminating in a proximal handle 12 and extending along an axis to a distal tip 16. At the distal tip 16, a plurality of distal electromagnetic sensing coils 33, 35 and/or 39 are positioned. At least one other electromagnetic sensing coil 37 is positioned in the proximal handle 12. The sensing coils operate together to permit navigation through lung tissue and for reporting the location of said catheter distal tip 16 in said lung tissue. A cylindrical ultrasound transducer array 30 is also located within the distal tip 16 and is configure for transmitting and receiving ultrasonic energy such as in the manner described above and shown in FIGS. 4, 6 and 7.

The cylindrical ultrasound transducer array 30 operates in a first imaging mode to acquire an image of a first target area located in a first target plane, and for defining a second target area located in said first target plane comprising a reduced second target area smaller than said first target area, such as is shown in FIG. 6 and described in greater detail above. The cylindrical ultrasound transducer array 30 also operates in a second, backscatter mode, to evaluate the spectral characteristics of acoustic energy reflected from said second target area such as in the manner shown in FIG. 7 and forming a quantitative ultrasound data set.

The catheter assembly is part of a system, such as is illustrated in FIG. 5, that also includes a navigation system/ultrasound display to present navigation, location and ultrasound data to said physician user.

The many features and advantages of the invention are apparent from the above description. Numerous modifications and variations will readily occur to those skilled in the art. Since such modifications are possible, the invention is not to be limited to the exact construction and operation illustrated and described. Rather, the present invention should be limited only by the following claims. 

What is claimed is:
 1. A medical device for operation by a physician user, in a patient's lung tissue having a suspected tumor, the medical device comprising: a) a catheter having an elongate catheter body terminating in a proximal handle and extending along an axis to a distal tip, said elongate catheter body adapted for delivery to lung tissue by insertion through a percutaneous needle; b) a plurality of electromagnetic sensing coils, located within said distal tip; c) at least one electromagnetic sensing coil in said proximal handle; said sensing coils operating together to permit navigation through lung tissue and for reporting the location of said catheter distal tip in said lung tissue; d) a cylindrical ultrasound transducer array located within said distal tip for transmitting and receiving ultrasonic energy, said cylindrical ultrasound transducer array operating in a first imaging mode to acquire an image of a first target area located in a first target plane and to define a second target area located in said first target plane comprising a reduced second target area smaller than said first target area; e) said cylindrical ultrasound transducer array operating in a second backscatter mode to evaluate the spectral characteristics of acoustic energy reflected from said second target area forming a quantitative ultrasound data set; f) a navigation system/us display to present navigation, location and ultrasound data to said physician user.
 2. A method of diagnosing a region of interest within lung tissue of a patient comprising the steps of: a) passing a catheter through a percutaneous needle to access said lung tissue, the catheter comprising: i) an elongate catheter body including a longitudinal axis and a distal tip and a proximal handle, ii) at least two distal electromagnetic sensing coils located within said distal tip, iii) at least one proximal electromagnetic sensing coil located in the proximal handle, and iv) a multi-element cylindrical ultrasound transducer array located within said distal tip, the cylindrical ultrasound transducer array positioned parallel to the longitudinal axis of said catheter body; b) navigating said distal tip of the catheter to a first location proximal to the region of interest using a navigation system that interacts with the distal and proximal electromagnetic sensing coils; c) in a first imaging mode, transmitting from the cylindrical ultrasound transducer array first ultrasound energy into the region of interest in a first target plane; d) receiving the first ultrasound energy from the transducer array at an imaging system; e) at the imaging system, creating an image of the region of interest along the first target plane, the image showing an anatomic structure, said anatomic structure selected from a set of structures comprising airways and blood vessels; f) identifying a second target area within the first target plane comprising a reduced second target area smaller than said first target area; g) in a second imaging mode transmitting second ultrasound energy from the transducer array into the reduced second target area; h) receiving the second ultrasound energy from the transducer array at a backscatter evaluation system; i) at the backscatter evaluation system, evaluating the acoustic spectra of the received second ultrasound energy to form a quantitative ultrasound data set. 